The first vertebrates to evolve were?

This is still in dispute, however, most scientist believe it was a creature from the Cambrian period of the Paleozoic era that we call the Pikaia. It wasn't a fish, but as potentially the first vertebrate, fish probably evolved form it. Some scientists theorize that it was a kind of worm. It had a backbone-like structure and shared other traits most commonly found in vertebrated such as: It was bilaterally symetrical, its head was distinct from its body, and its eyes were in the front of its head.